Key from String in Java RSA

Question

I am using in my app RSA cryptography. To store generated public key I convert it to String and then save it in database.

    Key publicKey=null;
    Key privateKey=null;

    KeyPair keyPair=RsaCrypto.getKeyPairRSA(1024);
    publicKey=keyPair.getPublic();
    privateKey=keyPair.getPrivate();



    String publicK=Base64.encodeToString(publicKey.getEncoded(), Base64.DEFAULT);
    String privateK=Base64.encodeToString(privateKey.getEncoded(), Base64.DEFAULT);

I save Strings publicK and privateK. My problem is, when I want to encrypt/decrypt text with RSA and use my saved Key in String format I don't know how to convert it to Key.

public static String encrypt(Key publicKey, String inputText){
    byte[]encodedBytes=null;
    String encryptedText="";
    try {
        Cipher cipher=Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        encodedBytes=cipher.doFinal(inputText.getBytes());
    } catch (Exception e) {Log.e("Error", "RSA encryption error");  }

    encryptedText=Base64.encodeToString(encodedBytes, Base64.DEFAULT);
    return encryptedText;
}

Do you have any idea? Thanks a lot

Please, please, please do not store unencrypted private keys in your database. If you have to store private keys that's known as escrowing and you should be encrypting them with a symmetric key only known to your application. — Kyle
– Kyle, Commented Apr 6, 2014 at 22:27
Thank you, yes I am thinking about it. Could you give me an advice, what is the best way to store a key in app?thanks — rgreso
– rgreso, Commented Apr 6, 2014 at 22:56
use a password protected Java keystore. Look up Java keytool... — Kyle
– Kyle, Commented Apr 7, 2014 at 0:56

Mark W · Accepted Answer · 2016-11-11 12:44:37Z

14

To convert publicK(String) to Public Key do as below :

byte[] keyBytes = Base64.decode(publicK.getBytes("utf-8"));
X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey key = keyFactory.generatePublic(spec);

To convert privateK(String) to Private Key do as below :

byte[] keyBytes = Base64.decode(privateK.getBytes("utf-8"));
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey priv = fact.generatePrivate(keySpec);

edited Nov 11, 2016 at 12:44

Mark W

5,98417 gold badges62 silver badges101 bronze badges

answered Apr 6, 2014 at 22:21

baldguy

2,0821 gold badge16 silver badges26 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

rgreso Over a year ago

thanks for answer. Eclipse shows me an error: The method decodeBase64(byte[]) is undefined for the type Base64. Could you help me with it please? thanks a lot

rgreso Over a year ago

Thanks for answer but it still shows an error, this time it wants another parameter: The method decode(byte[], int) in the type Base64 is not applicable for the arguments (byte[]) . Do you have any idea? Thanks a lot for your time

txedo Over a year ago

You can use Base64.encodeBase64String(byte[]) from Apache Commons Codec project.

Dean Blakely Over a year ago

I'm trying to do the same thing but PrivateKey priv = fact.generatePrivate(keySpec); gets InvalidDeySpecException saying I must use RSAPublicKeySpec but that won't take a byte[] as a parm

Danylo.Vus Over a year ago

try to change byte[] keyBytes = Base64.decode(privateK.getBytes("utf-8")); with byte[] keyBytes = Base64.decode(privateK, Base64.DEFAULT);

Robin Kanters · Accepted Answer · 2017-03-23 12:34:44Z

0

I can only assume the line:

PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(clear);

with "clear" was meant to be "keyBytes"

edited Mar 23, 2017 at 12:34

Robin Kanters

5,1372 gold badges23 silver badges36 bronze badges

answered Jul 23, 2015 at 2:34

user3005339

592 silver badges5 bronze badges

Collectives™ on Stack Overflow

Key from String in Java RSA

2 Answers 2

5 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related